This invention relates generally to materials for stickers, labels, adhesive tapes, and the like and more particularly to a new and advanced stock paper of laminated structure and highly desirable characteristics for use in stickers, labels, and the like.
Among labels, stickers, adhesive tapes, sticker tapes, and the like, there are those of the type wherein the front or display surface of a stock paper sheet is printed with desired inscriptions or marks, while the reverse surface is coated with an adhesive material and temporarily adhered to a backing paper sheet, and the stock paper is pulled apart from the backing paper at the time of use and adhered to the objective surface.
The "stock paper" and "backing paper" in this case are not restricted to ordinary cellulosic papers but, in certain cases, may be synthetic resin films, cellophane, metal foils, and other film and sheet materials. As a substitute for cellulosic papers, so-called synthetic papers produced by rendering synthetic resin films into papery form are known, and such synthetic papers can also be used as adhesive stock paper as described above and, of course, can be used also as backing papers.
For the adhesive, any of the various kinds of adhesives, particularly pressure-sensitive adhesives can be used. Example of suitable adhesives are elastomeric materials such as natural or synthetic rubbers, acrylic polymers, and rosin derivatives in solution or in an aqueous emulsion optionally containing some additives such as fillers, plasticizers and other modifiers. The solution or emulsion can be applied directly onto the adhesive stock paper or first onto the backing film and then transferred to the adhesive stock paper.
One group of synthetic papers, known as filler-void-whitened synthetic papers, is produced in each instance by stretching a film of a synthetic paper in which a fine filler has been blended to cause the formation of minute voids or microvoids and thereby to produce a material of a papery nature. The microvoids in the vicinity of the surface are communicative with the outside. While the synthetic resin film in this case may be of a single-ply or of a multiple-ply structure, it is desirable that the filler content of the papery surface be high, and that the elongation due to stretching be large, whereby the void content will be high in order to obtain good papery characteristics, particularly good printability.
While a synthetic paper of this filler-void-whitened type can also be used, for course, as an adhesive stock paper, inconvenience may be encountered in some cases depending on the kind of adhesive and/or adhesiveness of the backing paper surface, which may be considered to be non-adhesive. More specifically, a large number of microvoids are formed on the surfaces of the filler-void-whitened synthetic paper in order to improve the paperiness thereof. However, this results in a relatively low surface strength, and, consequently, the stock paper in some cases is ripped when being peeled apart from the backing paper and cannot be separated completely as a whole piece from the backing paper.